Add Outline stage, parallel reading, offline saves, backup, sync-conflict handling and more

Study
- New Outline stage (hierarchical I./A./1. points, linked to chunks, in all exports);
  the chunk stage is now "Chunks"
- Home cards: passages shown as ranges, tags capped with "+N more"

Reader
- Side-by-side translations and a Compare tab per verse
- Typeface, line spacing, verse-number settings; text and column scale with the screen
- Highlights/bookmarks sheet with named colours (synced); BSB footnote spacing fix
- Cmd-K palette (passages, studies, notes, marks), keyboard shortcuts and "?" help

Flow and safety
- Toasts with Undo replace most confirm()/alert()
- Back/Forward move between pages
- Server refuses saves over a newer copy (409); keep-mine / use-other banner;
  opening a study no longer re-stamps it
- Latest chapter request wins when flipping quickly

Offline and data
- Save books, plan days or a whole BSB/NET for offline
- Service worker fixes: helloao /api/ URLs were skipped and responses cloned too late
- Settings: download/restore a full backup

Accessibility
- Sheets trap focus and close on Escape, skip link, focus ring, reduced motion,
  theme contrast raised to 4.5:1 (with a test)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/components/reader/NavigatorSheet.jsx

@@ -2,12 +2,13 @@
 import { useState } from 'react';
 import Sheet from './Sheet.jsx';
 import { bookOptions, CHAPTER_COUNTS } from '../../utils/bibleUtils.jsx';
-import { READER_TRANSLATIONS } from '../../hooks/useBibleReader.js';
+import { READER_TRANSLATIONS } from '../../utils/bibleText.js';
+import { SaveBookOffline } from '../OfflineSave.jsx';
 
 const NT_START = bookOptions.findIndex((b) => b.abbrev === 'MAT');
 const chip = 'rounded-lg border px-2 py-2 text-center text-sm transition';
 
-export default function NavigatorSheet({ open, onClose, bookAbbrev, chapter, translation, onTranslation, translationNote, onGo }) {
+export default function NavigatorSheet({ open, onClose, bookAbbrev, chapter, translation, onTranslation, translationNote, onGo, offline }) {
   const [pickedBook, setPickedBook] = useState(null); // book abbrev whose chapters are showing
   const close = () => { setPickedBook(null); onClose(); };
   const book = pickedBook ? bookOptions.find((b) => b.abbrev === pickedBook) : null;
@@ -20,7 +21,7 @@ export default function NavigatorSheet({ open, onClose, bookAbbrev, chapter, tra
   );
 
   return (
-    <Sheet open={open} onClose={close} title={book ? (
+    <Sheet open={open} onClose={close} label="Go to" title={book ? (
       <button type="button" onClick={() => setPickedBook(null)} className="text-[var(--r-sub)] hover:text-[var(--r-text)]">‹ All books · <span className="text-[var(--r-text)]">{book.name}</span></button>
     ) : 'Go to'}>
       {!book && (
@@ -41,6 +42,7 @@ export default function NavigatorSheet({ open, onClose, bookAbbrev, chapter, tra
         </>
       )}
       {book && (
+        <>
         <div className="grid grid-cols-6 gap-1.5 sm:grid-cols-8">
           {Array.from({ length: CHAPTER_COUNTS[book.abbrev] ?? 1 }, (_, i) => i + 1).map((n) => (
             <button key={n} type="button" onClick={() => { onGo(book.abbrev, n); close(); }}
@@ -49,6 +51,8 @@ export default function NavigatorSheet({ open, onClose, bookAbbrev, chapter, tra
             </button>
           ))}
         </div>
+        {offline && <SaveBookOffline offline={offline} translation={translation} book={book.abbrev} name={book.name} />}
+        </>
       )}
     </Sheet>
   );